The invention relates generally to devices, systems and methods for the compression and/or expansion of a gas, such as air, and/or the pressurization of a liquid, such as water, and particularly to such a device that includes a rolling piston seal.
Known devices and systems can include a cylindrical housing with a movable piston disposed therein. Some known devices include the use of a gas, such as air, to move the piston to produce an output of work. Some pneumatic devices are used to compress and/or expand a gas, such as air. For example, a piston can be moved within a cylinder to push or move the gas out of the cylinder at an increased pressure. Such a device can be used, for example, in a compressed air energy storage system. Other devices can be used to pressurize a liquid, such as water, and/or pump the pressurized liquid, by applying force/work to a piston disposed within a cylinder in contact with the liquid. Such devices, or other devices, can also produce an output of work by urging pressurized liquid into the cylinder and against the piston.
In some known devices, a seal is disposed, for example, between an outer surface of the piston and an inner surface of the cylinder, to provide a fluid-tight seal between the piston and the cylinder wall. Various types of seals can be used, such as, for example, o-rings disposed on an outer surface of the piston and/or disposed on an inner surface of the cylinder, such that the piston can move relative to the cylinder while still maintaining a fluid-tight fit. However, use of traditional o-ring type seals can still require precision machining on the inner surface of the cylinder to produce a good seal and minimize wear on the o-ring, and can generate frictional losses caused by the sliding contact between the o-ring and the surface against which it seals (e.g. the cylinder wall), resulting in energy loss through heat. Some known devices that use fluid to move the piston to produce an output can include what is referred to as a rolling seal or a rolling diaphragm disposed between the piston and the cylinder wall.
In a compressed air energy storage system, the pressure vessel(s) or cylinder(s) in such systems can be very large in diameter, particularly at the early stages of a compression process. A rolling seal may be useful in such systems to compress and/or expand gas. For example, forming a precision machined surface on the interior of a large pressure vessel sufficient to receive a movable piston with a fluid-tight seal can be difficult and costly. For example, a pressure vessel may need to undergo a honing and chroming process to create a suitable surface to enable a smooth yet fluid-tight sliding movement of the piston within the pressure vessel. Thus, there is a need to provide improved sealing mechanisms in devices, such as pneumatic devices used to compress and/or expand air. There is also a need to improve the performance of known rolling seals.